A spacecraft such as a satellite, spaceship, and the like, can be placed in orbit around the Earth with the aid of a launch vehicle. The launch vehicle can be launched either from a fixed launch pad, a floating launch pad or from a flying aircraft (i.e., air-launched). When it is required to place the spacecraft in a specific orbital plane relative to the stars, the opportunity to launch is limited to a very short period (i.e., launch window). Launching a launch vehicle from a fixed launch pad within the launch window depends on a number of factors, such as the time required to prepare the launch pad, assembling the launch vehicle on the launch pad, placing the spacecraft on the launch vehicle, loading the propellant into the launch vehicle, verifying proper operation of the systems and performing the launch.
The minimum orbital inclination which can be achieved from a fixed launch pad is rather restricted and depends on the geographic latitude at which the fixed launch pad is located. On the other hand maintaining a launch crew on site and repeatedly performing the pre-launch operations, increases the cost of the launch significantly.
Launching a launch vehicle from an aircraft overcomes most of the difficulties mentioned herein above. For example, by flying the aircraft together with the launch vehicle at a suitable latitude and speed, the chances of missing the launch window are significantly reduced. In this case, the launch window is limited only to the time which the aircraft can remain airborne. Furthermore, the minimum orbital inclination is not as restricted as in the case of fixed launch pads, and highly inclined orbits can be achieved.
Since the launch vehicle is launched from an altitude much higher than in the case of a fixed launch pad, less potential energy has to be added to the launch vehicle, less fuel has to be carried by the launch vehicle and thus a heavier payload can be placed into orbit. The launch location can be selected so that no inhabited land mass is jeopardized in launching the launch vehicle. Employing an aircraft to launch a launch vehicle is equivalent to having one launch pad which can be easily moved to any desired geographical location. Methods and systems for launching a launch vehicle from an aircraft are known in the art.
U.S. Pat. No. 6,474,600 issued to Apps and entitled “Aircraft Fuselage Having a Rear-End Opening for Cargo Dispatch”, is directed to a fuselage of an aircraft having a rear end and a cargo carrying compartment, the aircraft carrying a cargo and dispatching the cargo in mid-air. The rear end of the fuselage includes a plurality of frames, a keel beam, a rear pressure bulkhead, two aft openings, a set of upper rails and a set of side rails. The rear pressure bulkhead includes two fore openings and a first set of doors. Each of the two fore openings includes a seal. The two aft openings are located at the underside of the fuselage. The two aft doors are closable by means of a second set of doors.
The rear pressure bulkhead separates the rear end of the fuselage from the cargo carrying compartment of the aircraft. The cargo carrying compartment is pressurized. When the first set of doors are in closed position, the pressure in the cargo carrying compartment presses the first set of doors against the seals to seal the cargo carrying compartment against the rear end of the fuselage. Each set of the upper rails and the set of the side rails are located on each side of the keel beam. The set of the upper rails and set of the side rails extend between the cargo carrying compartment and the two aft openings.
The set of upper rails and the set of side rails support and guide the respective items of a cargo. The set of the upper rails and the set of the side rails are inclined downwards at an angle to the straight and level flight path of the aircraft, in order to allow the items of the cargo to travel downward under gravity away from the rear pressure bulkhead, to be dispatched through the two aft openings. The cargo has a relatively small transverse dimension compared to the length thereof. The two fore openings provide passageway for the cargo. The item of the cargo depends from the relevant set of upper rails as the item moves toward the associated set of the aft openings. The associated set of side rails provides sideways support for the item as the cargo travels rearward.
The two fore openings provide unobstructed access to the cargo carrying compartment from outside the rear pressure bulkhead. The cargo is loaded in the cargo carrying compartment through an elongate opening near the front of the fuselage. The aircraft flies at a normal cruising altitude to a zone where the cargo is to be dispatched. The aircraft descends to an altitude at which the fuselage can be depressurized. One or both of the first set of doors are raised into an open position and the item of the cargo is lifted and conveyed from the cargo carrying compartment to the set of the upper rails and the set of the side rails. The second set of doors are opened and the item of the cargo is moved along the set of the upper rails and the set of the side rails, and the item of the cargo is dispatched.
U.S. Pat. No. 5,279,199 issued to August and entitled “Technique and Apparatus for Rearward Launch of a Missile”, is directed to a method for launching a missile from an aircraft. The aircraft includes a missile launch tube located under a wing thereof. The missile is located within the missile launch tube. The forward end of the missile launch tube is closed and external portion thereof aerodynamically formed. The rear end of the missile launch tube is sealed with a break-away membrane. An air bag is located between the nose of the missile and the forward end of the missile launch tube. A missile nose bra is positioned within the air bag over the nose of the missile.
To initiate the launch of the missile, the air bag is inflated and a breaker device is activated to break the break-away membrane. The expansion force of the air bag shoots the missile out of the missile launch tube, in a direction opposite to the flying direction of the aircraft. Engagement of the missile nose bra with the missile, ensures that the longitudinal axis of the missile will match the longitudinal axis of the missile launch tube upon expulsion from the missile launch tube.
U.S. Pat. No. 6,508,435 issued to Karpov et al., and entitled “Method for Controlling an Aerospace System to Put a Payload into an Orbit”, is directed to a method for putting a payload in an orbit. A carrier aircraft with a launch vehicle on board, takes off form a base aerodrome. The launch vehicle includes a payload. When the carrier aircraft reaches the launch area, it switches to the maximum cruising speed mode. The aircraft carrier begins a pitch-down maneuver and the flight speed increases to the maximum permissible horizontal speed. At this point the carrier aircraft switches to the pitch-up mode to fly at the maximum permissible angle of attack, where a near zero g-load acts on the carrier aircraft. At a preset time when the design flight speed, the design flight altitude, the design trajectory pitch angle and the near zero g-load conditions are satisfied, the launch vehicle is separated from the carrier aircraft with a predetermined speed of lagging relative to the carrier aircraft.
When the launch vehicle separates from the carrier aircraft and is located at a predetermined safe distance, the launch vehicle executes a pitch-around maneuver, until the optimum pitch angle is reached to launch the launch vehicle with the payload to a scheduled point of trajectory flight. When the optimum pitch angle differs from the vertical by 10 degrees and 30 seconds, active flight of the launch vehicle first stage is effected, followed by the separation of the launch vehicle first stage. Then the fairing separation, final stage burn-out and separation of the payload from the launch vehicle are effected.
When the launch vehicle is ejected from the carrier aircraft, the carrier aircraft flies toward the landing aerodrome. In case the separation of the launch vehicle from the carrier aircraft is aborted, the carrier aircraft together with the launch vehicle and the payload flies toward the landing aerodrome. In order to ensure the safety of the carrier aircraft and the crew members thereof, the launch vehicle propellant and the payload propellant are jettisoned overboard and the carrier aircraft lands with empty launch vehicle tanks and empty payload tanks.
U.S. Pat. No. 4,901,949 issued to Elias and entitled “Rocket-Powered, Air-Deployed, Lift-Assisted Booster Vehicle for Orbital, Supraorbital and Suborbital Flight” is directed to a rocket vehicle which is air-launched from a carrier aircraft. The rocket vehicle includes a first stage, a second stage, a third stage, an aerodynamic wing, a plurality of fins, a plurality of fin actuators and an aft skirt. The first stage includes a first stage rocket motor, a first stage nozzle and a first stage casing. The second stage includes a second stage rocket motor, a second stage nozzle and a second stage casing. The third stage includes a third stage rocket motor, a third stage nozzle, a third stage casing and a payload. The aft skirt is secured to the first stage casing.
The first stage and the second stage are joined by a first adaptor. The second stage and the third stage are joined by a second adaptor. The aerodynamic wing is secured to the first stage casing. The fin actuators are located in the aft skirt. The fins are mechanically and pivotally supported by the fin actuators. The rocket vehicle is mounted to the carrier aircraft via an underwing launch pylon and a release mechanism.
The carrier aircraft takes off from a conventional runway. When reaching a launch point, the rocket vehicle is air-launched from the carrier aircraft at subsonic velocities in a substantially horizontal attitude and the rocket vehicle performs a free-fall maneuver. The first stage motor ignites and the fins are placed in a configuration which produces a pitch-up attitude of the rocket vehicle. In this manner, the rocket vehicle performs a vertical-S maneuver and climbs at an angle of ascent which is less than 45 degrees. The fins are placed in a configuration to cause the rocket vehicle to pitch-down, thereby decreasing the ascent flight path thereof and reaching a push-over point. The push-over point is related to an optimum attitude and velocity of the rocket vehicle. The first stage, the aerodynamic wing, and the fins are jettisoned and burn up in the atmosphere on reentry. Likewise the second stage ignites and is jettisoned and the third stage ignites and is jettisoned.
U.S. Pat. No. 5,363,737 issued to Wallis and entitled “Air-Vehicle Launcher Apparatus”, is directed to a system for launching a missile from an aircraft. The system includes a launcher, an adaptor, a series of attachment hooks and a plurality of releasable straps. The missile includes a plurality of deployable fins. The adaptor includes an empennage, a deployable parachute and jettison means.
The launcher is attached to the underside of the aircraft. The adaptor is attached to the launcher by the attachment hooks. The deployable parachute and the jettison means are stowed inside the adaptor. The missile is connected to the adaptor by the releasable straps. When the adaptor and the missile separate from the aircraft, the missile together with the adaptor adopts a pitch-down attitude while the empennage deploys. The deployable fins and the deployable parachute begin to deploy. The empennage and the deployable parachute stabilize the flight of the missile, while the deployable fins extend to lock-out positions. The adaptor and the missile are separated by the action of the jettison means and with the aid of the deployable parachute, and the missile continues flying toward a target.
Reference is now made to FIGS. 1A, 1B, 1C and 1D. FIG. 1A is a schematic illustration of a system generally referenced 50, for air-launching a missile generally referenced 52, as known in the art, the system and the missile being carried inside an aircraft generally referenced 54. FIG. 1B is a schematic illustration of the stages in air-launching the missile of FIG. 1A. FIG. 1C is a schematic illustration of a bottom view (view A) of the system of FIG. 1B in perspective, during the transition from stage II to stage II. FIG. 1D is a schematic illustration of a top view (view B) of the system of FIG. 1B in perspective, at stage III. The air-launch stage of missile 52 as illustrated in FIG. 1A, is known in the art as the zero stage (i.e., the stage in which aircraft 54 carries missile 52 to a region suitable for launching missile 52).
With reference to FIG. 1A, system 50 includes a platform 56, one or more ejection parachutes 58, four maneuvering parachutes 60, a plurality of cables 62 and a detachable ring 64. Missile 52 includes a fore section 66 and an aft section 68. Detachable ring 64 (FIG. 1C) is connected to a bottom lateral side of platform 56. Ejection parachutes 58 is connected to an end (not shown) of platform 56, in the vicinity of fore section 66. One end of cables 62 is connected to bottom four corners (not shown) of platform 56, and the other end thereof is connected to maneuvering parachutes 60. Cables 62 pass through detachable ring 64.
Aircraft 54 is flying in a direction designated by an arrow 70 relative to a global coordinate system. System 50 and missile 52 are located within aircraft 54, such that the direction from aft section 68 to fore section 66 is opposite to the direction of arrow 70. Ejection parachutes 58 and maneuvering parachutes 60 in FIG. 1A are shown in a packed condition.
With reference to FIG. 1B, in stage I, ejection parachutes 58 is deployed, thereby pulling platform 56 and missile 52 out of aircraft 54, in a direction designated by an arrow 72 relative to aircraft 54. In stage II platform 56 and missile 52 drop in the air, while maneuvering parachutes 60 are deployed. This configuration of platform 56 and missile 52 in which platform 56 is located below missile 52 is unstable. Therefore, platform 56 and missile 52 have a tendency to roll about a longitudinal axis 74 (FIG. 1C) of platform 56, to transform to a configuration in which platform 56 is located on the top of missile 52.
With reference to FIG. 1C, maneuvering parachutes 60 apply a force to a lateral side of platform 56, at the joint between detachable ring 64 and platform 56. The product of this force and the distance between detachable ring 64 and longitudinal axis 74, produces a moment which rotates platform 56 and missile 52 about longitudinal axis 74, in a direction referenced by an arrow 76. Thus, the force of maneuvering parachutes 60 aids in performing the rolling motion about longitudinal axis 74.
In stage III (FIGS. 1B and 1D) detachable ring 64 is disconnected from platform 56, wherein maneuvering parachutes 60 apply a uniform force on platform 56 through the four corners of platform 56. This uniform force moves platform 56 and missile 52 to an orientation suitable for launching missile 52 (stage IV). In stage V platform 56 separates from missile 52 and a rocket motor (not shown) of missile 52 is ignited, thereby launching missile 52. Platform 56 falls to the ground or to the ocean in reduced speed, with the aid of maneuvering parachutes 60.
Reference is now made to FIG. 1E, which is a schematic illustration of air-launching a missile generally referenced 80, from a flying aircraft generally referenced 82, as known in the art. Missile 80 includes a first stage 84, a second stage 86 and a payload (not shown). Missile 80 is connected to a bottom section 88 of a fuselage 90 of aircraft 82 by a plurality of pylons 92. Each of pylons 92 includes a disengagement mechanism (not shown) to decouple missile 80 from aircraft 82. First stage 84 includes a plurality of fins 94.
In stage zero, when aircraft 82 reaches the launch site, the disengagement mechanisms are activated, thereby decoupling missile 80 from aircraft 82. In stage I fins 94 are operated in order to maneuver missile 80 to a launch orientation designated as stage II. In stage II, first stage 84 is ignited thereby launching missile 80. In stage III, first stage 84 is decoupled from second stage 86, and in stage IV second stage 86 is ignited.